On-line multibed sorption trap and injector for the GC analysis of organic vapors in large-volume air samples.
On-line multibed sorption trap and injector for the GC analysis of organic vapors in large-volume air samples.
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DOI：
10.1021/ac020575
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发表时间：
2003-01
影响因子：
7.4
通讯作者：
Juan M. Sanchez;R. Sacks
中科院分区：
文献类型：
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作者：
Juan M. Sanchez;R. Sacks
一个毛细管尺寸的在线吸附捕集器被用来预浓缩有机蒸气从大体积的空气样品和注入的有机化合物到分离柱作为一个相对狭窄的蒸汽塞。多床阱由钴镍合金制成，用于样品解吸期间的电阻加热，并使用四种不同的碳基吸附材料，这些材料在样品预浓缩期间沿样品气流方向从最弱到最强分级。然后将流动方向反转以进样。多床设计和热解吸过程中的流动方向反转防止样品中的高沸点化合物到达最强的吸附材料，从那里它们将难以作为足够窄的蒸气塞解吸。使用相对高的电流脉冲来快速实现200-400摄氏度温度范围内的阱温度，并且使用较低的电流来维持最高温度几秒钟，以确保注入整个捕获的样品。在1.5秒后达到350摄氏度的温度，并且注入塞宽度通常在0.6-1.3秒的范围内。峰面积与样品采集时间的曲线图显示出极好的线性，且注射间相对标准偏差约为+/-5%。性能数据为42挥发性化合物的混合物，挥发性范围从n-C5到n-C12。提供了极性和非极性化合物的注入塞宽度和形状的数据。在高于300 ℃的注射温度下观察到热不稳定化合物的分解。
A capillary-dimension on-line sorption trap is used to preconcentrate organic vapors from large-volume air samples and inject the organic compounds into the separation column as a relatively narrow vapor plug. The multibed trap is made from a Co-Ni alloy for resistive heating during sample desorption and uses four different carbon-based adsorption materials that are graded from weakest to strongest in the direction of the sample gas flow during sample preconcentration. The flow direction then is reversed for sample injection. The multibed design and the flow direction reversal during thermal desorption prevents the higher-boiling-point compounds in the sample from reaching the strongest adsorbing material, from which they would be difficult to desorb as a sufficiently narrow vapor plug. A relatively high current pulse is used to rapidly achieve trap temperatures in the 200-400 degrees C temperature range, and a lower current is used to maintain the maximum temperature for several seconds in order to ensure injection of the entire trapped sample. A temperature of 350 degrees C is reached after degrees 1.5 s, and injection plug widths are typically in the range of 0.6-1.3 s. Plots of peak area versus sample collection time show excellent linearity and shot-to-shot relatively standard deviations of about +/- 5%. Performance data are presented for a mixture of 42 volatile compounds spanning a volatility range from n-C5 to n-C12. Data are presented for injection plug width and shape for both polar and nonpolar compounds. Decomposition of thermally labile compounds is observed for injection temperatures above 300 degrees C.